There are numerous types of fuel injection systems in use in internal combustion engines. In one type, the quantity of fuel injected by an injector in each operating cycle of the engine is controlled by the pressure of the fuel supplied to the injector. Such an arrangement has proven to be very advantageous because the pressure may be easily adjusted in response to various engine operating parameters. While this type of system has been successfully used on relatively large engines for trucks, such past systems have required relatively expensive and complicated parts, which has made them unsatisfactory for use in smaller relatively low cost engines.